from gi.repository import Gtk


def on_fileentry_file_set(entry):
    print entry.get_filename()
    print entry.get_filenames()
    print entry.get_files()

fileentry = Gtk.FileChooserButton()
fileentry.connect('file-set', on_fileentry_file_set)

window = Gtk.Window()
window.add(fileentry)
window.show_all()
window.connect('delete-event', lambda *args: Gtk.main_quit())

Gtk.main()
